Many flame retarding agents and methods of application have been developed in attempts to obtain flame resistant textile materials and thermoplastic or thermosetting resin compositions.
Flame retardant textiles have been produced by depositing metal oxides, within or on the textile fibers, by the successive precipitation of ferric oxides and a mixture of tungstic acid and stannic oxide or by successive deposition of antimony trioxide and titanium dioxide. Such processes require plural treatment baths in which strongly acidic solutions are employed thus posing the problem of possible textile degradation. Furthermore, metal oxide coatings on textile materials create difficulties in subsequent dyeing processes which deleteriously affect the hand of the finished product. Another process involves the use of a single processing bath wherein a dispersion of a chlorinated hydrocarbon and finely divided antimony oxide is padded on the textile material. Near the textile combustion temperatures antimony oxide will react with hydrogen chloride, generated by degradation of the chlorinated hydrocarbon, to form antimony oxychloride which acts to suppress flame. This combination of a chlorinated hydrocarbon and finely divided antimony oxide are not acceptable finishes for closely woven textiles as they deleteriously affect the hand of the finished product. A further process for imparting flame resistance to cellulosic materials is by the esterification of the cellulose with diammonium hydrogen orthophosphate. Textile products so treated however are subjected to metathesis reaction with cations during washing, and must be regenerated by reacting the wash product with an ammonium chloride solution.
The product of thermoplastic resin compositions which are flame retardant is of considerable commercial importance. For example, such articles as castings, moldings, foamed or laminated structures and the like are required, or are at least desired, to be resistant to fire and flame and to possess the ability to endure heat without deterioration. The use of various materials incorporated into thermoplastic resins so as to improve the flame retardancy thereof has been known. Many compounds have been commercially available for such use, among them being chlorostyrene copolymers, chlorinated paraffin wax in admixture with triphenyl styrene, chlorinated paraffins and aliphatic antimonical compounds, as well as antimony oxide -- chlorinated hydrocarbon mixtures. A problem associated with these compounds has been however, the fact that generally a large amount, i.e. upwards of 35% of additive, must be incorporated into the resin in order to make it sufficiently flame retardant. Such large amounts of additive may deliteriously affect the physical characteristics of the thermoplastic resin, as well as substantially complicating and increasing the cost of preparation thereof. A further problem is that these prior art additives tend to crystallize or oil cut of the resin after a relatively short time of incorporation. The present invention relates to a group of compounds which may be added to thermoplastic resins in relatively small amounts and still produce satisfactory flame retardant compositions which will not crystallize nor oil out of the resin after incorporation therein.